In the past nursing bottles and cups for dispensing milk and other liquids to infants and children have often been in the form of vented covered containers. For instance, U.S. Pat. No. 2,372,281 to Jordan, which issued on Mar. 27, 1945, has a cover that provides a nipple on one side having flow-regulating means and a vent on the other side also having flow-regulating means. By adjusting the two flow-regulating means, the user can comfortably draw liquid from the nipple. As the liquid is withdrawn, air moves in through the vent to replace the withdrawn liquid and prevent negative pressure build-up which in the extreme can stop liquid flow.
Another covered drinking cup is disclosed in U.S. Pat. No. 2,608,841 to Rice which issued on Sep. 2, 1952. As the venting means, the Rice cup provides a manually adjustable valve which controls the ease with which air is admitted into the cup for venting. It thereby regulates the flow of liquid.
With respect to the admission of air into nursing bottles and the like, check valves have often been used and are disclosed in the U.S. Pat. Nos. 4,401,224 to Alonso which issued on Aug. 30, 1983; 4,545,491 to Bisgaard, et al. which issued on Oct. 8, 1985; 4,723,668 to Cheng which issued on Feb. 9, 1988; and 4,828,126 to Vincinguerra which issued on May 6, 1989.
Other vent means are disclosed in U.S. Pat. No. 4,865,207 to Joyner, et al. which issued on Sept. 12, 1989 in which a fabric hydrophobic filter passes air into the nurser.
U.S. Pat. No. 4,135,513 to Arisland, which issued on Jan. 23, 1979, discloses a drinking nozzle for a nursing bottle which incorporates air venting means, opening a valve when the pressure within the container is substantially less than atmospheric pressure to thereby vent the head space.
U.S. Pat. No. 5,079,013 to Belanger, which issued on Jan. 7, 1992, discloses a dripless liquid feeding/training container in which the cover is provided with two spring-biased check valves. One check valve is a spring biased ball check that permits inward air flow for venting and the other check valve is a spring-biased outlet valve that opens by the sucking action of the infant and springs closed when the sucking action relents. The container is described as "dripless".
One of the shortcomings of some of the prior art is that the valves involved have metal parts. Further, the number of the parts involved makes such containers difficult to manufacture, assemble and clean. There is, hence, a need for a less complicated structure that eliminates the metal parts, and is readily washable. It is to such a need that the present invention is directed. In a preferred embodiment, the control element has additional means to retain it in place in the cup even during impact.